Depth measurement in video scenery in general and Gesture Recognition are topic in computer science with goal of interpreting gestures of human or other bodies via specialized equipment and mathematical algorithms. Gestures may originate, for example, from any bodily motion or state. Some systems use two video stereo cameras together with a positioning reference such as a set of infrared emitters to enable automated recognition of the contour of a body in the field of view of the cameras and to identify certain movements of organs or portions of the body so that the identified movements or gestures may be used for communicating of the human with application running in communication with the gesture recognition system. Some of the systems using stereoscopic gesture identification rely on a process which pairs features of a first stereo video image with features of a second stereo video image.
Other systems may employ depth measurement of points on a body in the field of imaging (FOI) using a method known as Time of Flight (TOF), in which an irradiating source sends pulsed light towards the imaged body. The pulsed light travels to the body and is reflected back to a video camera that is equipped with a shutter to control the timing of receipt of light onto its sensor. Since the time takes to a reflected light from a point on the imaged body is relative to the distance (or depth) of that point from the camera, with proper synchronized gating light from the nearer point to be received at the sensor for a longer time longer than light that travels from a farther point on the body. Accordingly, the amount of energy (which may be represented as “grey level” in the 2-D buffer of the sensor) is inversely proportional to the distance of the point from the sensor. In order to compensate for variations in the reflectivity of different points on the body mathematical measures may be taken, such as normalizing the intensity based on an average intensity at point.
Depth measurement using TOF principals may also be done by calculating the distance of a point in the FOI by calculating the time that takes to a pulse of light to travel to the point and back to the sensor, and use this figure to calculate the distance (or depth) of that point. Another method of measuring depth of a point on an imaged body is by measuring the phase-shift of the reflected light when it is received by the sensor, with respect to the phase of the emitted light towards the body.
Some of the known methods which use a stereoscopic arrangement of cameras need also comparatively a large amount of computations in comparing the pictures taken from one camera to those taken by the other camera in order to pair together pictorial attributes of the two sets of pictures for creating calculated 3-D image out of the pairs of pictures based on the known location of the two cameras. Large amount is needed in such arrangements also in real time to solve the trigonometric equations involved in the establishment of a distance of a point. Naturally, the accuracy of such systems is highly influenced by the physical dimensions of the set of two cameras and especially the distance between the cameras, thus requirement for higher accuracy may impose larger physical dimensions of such systems.
Furthermore, use of methods such as stereoscopic gesture recognition is inherently inferior to other methods, such as depth measuring methods, for example measurement of time-of-flight (TOF) of a light pulse by a depth measuring arrangement and inclusion of that data into the graphical data of the picture, when it is required to recognize several body organs positioned close and in front of each other, such as a finger in front of a hand palm or in front of human face, or the like.
It may therefore be beneficial to have system and method which are capable of capturing and calculating 3-D imaging data of a body in the field of imaging of a 3-D capturing system which is accurate enough to allow distinction of organs positioned closely one in front of the other and that may maintain small physical dimensions regardless of the accuracy requirements and may require small amount of associated calculations.